Leaf spring



Dc. 16, 1952 c uRc L 2,621,921

LEAF SPRING Filed Aug. 3. 1948 IN VEN TOR.

mm/waflmymmw ATTORNEYS @MWM Patented Dec. 16, 1952 LEAF SPRING Harold E. Churchill, South Bend, Ind., assignor to The'Studebaker Corporation, South Bend, Ind., a corporation of Delaware Application August 3, 1948, Serial No. 42,161

3 Claims.

My present invention relates to an improvement in leaf springs, and more particularly to leaf springs embodying anti-friction means for reducing the amount of friction between adjacent leaves.

It is broadly old to provide leaf springs with anti-friction means between the surfaces of adjacent leaves, and my present invention is primarily concerned with a novel form of anti-friction means, and to novel means for incorporating such anti-friction means between the leaves, and particularly between the outer end portions of adjacent leaves.

It is an object of my invention to provide a leaf spring in which anti-friction means in the form of round metal pellets is disposed between one or more pairs of adjacent leaves of the spring.

By employing round metal pellets made, for example, of steel, a relatively large number of such pellets may be disposed between the adjacent leaves providing a large number of contact points of small area which serve admirably to reduce substantially the friction between the leaves.

A preferred feature of one embodiment of my invention resides in mounting the round metal pellets on tape members which may be readily and easily inserted between the outer end portions of adjacent leaves of the spring in fabricating the spring.

In the embodiment of my invention referred to the tape member has the pellets suitably secured to one of the surfaces thereof, and the other surface of the tape member is provided, preferably, with a coating of a pressure sensitive adhesive, so that the tape member may be applied to a spring by slight pressure engagement of the tape member with the spring. The tape member is preferably made of paper, cloth or the like, and it is not intended to last for the life of the spring. After the spring has been in use for a period of time, the metal pellets will have worn or formed slight grooves or depressions in the adjacent surfaces of the leaves of the spring which serve to retain the pellets in position between the leaves after the tape member has been destroyed.

A preferred feature of another embodiment of my invention is to provide for mounting of round metal pellets by means of a suitable adhesive directly to one surface of a leaf of the spring in position to be disposed between the latter leaf and an adjacent leaf of the spring.

In the form of my invention last referred to, the adhesive retains the metal pellets in position in assembling of the spring, and, as before, after the spring has been in use for a short time, retaining grooves are worn or formed in opposed surfaces of adjacent leaves which serve to retain the metal pellets in position.

The metal pellets in the above embodiments of my invention wear or cause the formation of grooves extending lengthwise of the spring leaves, and the metal pellets by their disposition in such grooves, prevent relative lateral movement of the ends of adjacent spring leaves to provide such additional advantage of my invention over previously known spring constructions.

Also, in the above referred embodiments of my invention the arrangement of the round metal pellets between the leaves form a reservoir means between the opposed surfaces of adjacent leaves which serve to retain lubricant for reducing friction between the metal pellets and the surface of the leaves.

In still another embodiment of my invention I propose to embed the round metal pellets in a resilient member made, for example, of rubber which is disposed between the end portions of a pair of adjacent spring leaves.

In the last noted form of my invention, the rubber layer provides a resilient cushion between the ends of the adjacent leaves, and the round pellets provide a multiplicity of small contact points between the opposed surfaces of adjacent leaves.

The above and other objects, features and advantages of my invention will appear from the detailed description.

Now in order to acquaint those skilled in the art with the manner of constructing and utilizing leaf springs in accordance with my present invention, I shall describe, in connection with the accompanying drawing, certain preferred embodiments of my invention.

In the drawing:

Figure 1 is a side elevational view of a leaf spring constructed in accordance with one embodiment of my invention.

Figure 2 is a side elevational view of the right hand end portions of the several leaves of the leaf spring of Figure 1 arranged in vertical spaced apart relation, and showing the manner in which, anti-friction means of my invention, embodying a mounting tape member is arranged betwee certain of the leaves of the spring.

Figure 3 is a view looking toward the concave surface at the outer end of one of the spring leaves with which the anti-friction means of my invention is embodied, with the view being taken substantially along the line 3-3 of Figure 2,

looking in the direction indicated by the arrows;

Figure 4 is an enlarged detail sectional View taken lengthwise of the end portion of a pair of adjacent leaves of the spring of Figure 1, and illustrating the manner in which the round metal pellets form openings in the tape member, and further, the manner in which the metal pellets are retained in grooves formed by the pellets in adjacent leaves of the spring;

Figure 5 is a transverse sectional view at the end portions of a pair of adjacent leaves of the spring of Figure 1, after the mounting tape member has been worn away;

Figure 6 is a side elevational view of the end portion of a spring leaf of another embodiment of my invention in which the metal pellets are applied by an adhesive directly to one of the surfaces of the spring; and

Figure '7 is a transverse sectional view of a spring leaf of still another embodiment of my invention in whichthe round metal pellets are carried in a rubber layer applied at the end of a spring leaf.

Referring now to the drawing, I have shown, in Figure 1, a leaf spring constructed in accordance with one embodiment of my invention, comprising a plurality of conventional substantially concavo-convex spring leaves arranged in stacked relation, and in which the several leaves 4 are of progressively diminishing lengths upwardly of the stack in the position of the spring shown in Figure 1. Suitable end plate members 5 and 6 are disposed adjacent the upper and lower leaves of the leaf spring and the several leaves are secured in assembled relation in the usual manner by nut and bolt means indicated generally at 1 extending substantially centrally of the ends of the leaves. The several leaves 4 are made of spring steel now presently in use for such purposes and form a spring of somewhat semi-elliptical form and in which the concavoconvex surfaces of the leaves gradually approach a straight line toward the upper end of the assembly, as shown in Figure 1.

According to my invention, I propose to embody anti-friction means 8 between the outer end portions of adjacent spring leaves of the leaf spring. The anti-friction means 8 of the embodiment shown in Figures 1 through 5 comprise a tape member 9 of paper or cloth or other suitable or like material, and has round metal pellets l0 suitably secured to one of the surfaces thereof by any suitable adhesive. The metal pellets 10 are preferably of a steel of harder composition than that of leaves t, and are arranged indiscriminately and cover substantially entirely the one surface of the tape member 9. One form of metal pellet suitable for use with my present invention is known commercially as S. A. E. standard P33, which is conventionally used in shot peening, and is identified at page 791 of the 1946 edition of the S. A. E. Hand Book. The tape member 9 may, for example, be made of 96/60 warp sateen which in a 40" width weighs 1.48 lbs. per yard, and the surface thereof, which carries the shot or metal pellets may be coated with an adhesive of regular reclaimed rubber of about .025 in thickness for securing the metal pellets IO thereto. The tape member 9 preferably has a suitable pressure sensitive adhesive on the other surface thereof for applying the tape member to the concave surface of a spring leaf adjacent the outer end thereof. This adhesive may, for example, be of the composition disclosed in Patent No. 2,217,273, and is sold in the open market under the trade name Permatex 2. Thus when the several leaves 4 of the spring are assembled, the metal pellets 10 of one leaf 4 are adapted to have engagement with the convex surface of the adjacent spring leaf, and more particularly as shown in Figure 2, with portions of the slightly tapering surfaces l2 at the outer ends of the convex surfaces of the leaves. After the spring has been in use a short time, the metal pellets i!) wear openings in the tape members 9 and form grooves, such as shown at H in Figure 4, in the opposed surfaces of adjacent leaves.

After continued use of the spring in a vehicle or the like the tape members 9 are caused to be worn away, as shown in Figure 5, but this does not occur until after the metal pellets I!) have formed retaining grooves in the opposed convex and concave surfaces of an adjacent pair of spring leaves. It is a characteristic of a leaf spring that the greatest amount of frictional engagement occurs between the long leaves of the spring, and as illustrated in Figure 2, the antifriction means 8 of my invention is embodied between the five long leaves of the spring, and while the anti-friction means of my invention may be embodied between the other of the spring leaves, it has been found in most instances that the provision of the anti-friction means between a few of the long leaves is adequate to eliminate the objectionable frictional rubbing between such leaves in the conventional form of such springs.

As previously mentioned, the metal pellets, in addition to providing anti-friction means between the ends of adjacent spring leaves, serve, by their disposition in the lengthwise grooves of adjacent leaves, to prevent relative lateral movement of the outer end portions of adjacent leaves' In the embodiment of my invention shown in Figure 6, the round metal pellets I0 are applied directly to the end portions of one surface of the spring leaf 4', and preferably to the tension side of the spring. Preferably a layer or coating of suitable adhesive is applied to the surface of the spring leaf 4, and the metal pellets 16 are then applied in any suitable manner to the layer or coating of adhesive. The adhesive retains the metal pellets in assembling of the several leaves having the metal pellets applied to the end portions thereof, and as in the embodiment first described, grooves are formed by the pellets in the opposed surfaces of adjacent leaves which serve as retainers for the metal pellets. The previously mentioned adhesive Permatex 2 has been found to be suitable for securing the metal pellets in directly to the leaves of this embodiment of my invention.

In both of the above described embodiments of 'my invention, the metal pellets space the adjacent ends of a pair of spring leaves away from each other, and the metal pellets together with the opposed surfaces of the leaves and the grooves therein provide a reservoir means for retaining lubricant between the leaves for lubricating the bearing surfaces of the leaves and the metal pellets all to the end of substantially reducing friction between adjacent leaves and the pellets therebetween.

Referring now to Figure 7, the embodiment of my invention therein shown comprises a rubber panel or member I 4 in which a large number of round metal pellets I5 are embedded. The rubber panel may, for example, be of a length of 6 inches and of a width substantially equal to the width of the spring leaf H which, as before, comprises one leaf of a plurality of leaves making up the spring. In one construction embodying this form of my invention the panel member [5 was made of reclaimed rubber and was of a thickness of .031 inch. Preferably, to facilitate handling of the member [4 to aid in embedding of the metal pellets therein, one surface of the panel member is calendered on Holland cloth. The unprotected surface of the panel member may then be made sticky or tacky by swabbing with a suitable solvent, such as naphtha. The metal pellets are applied to the tacky surface. This may be accomplished by drawing the panel l4 under a mandrel disposed above a container holding a supply of the metal pellets. In this manner the tacky surface of the panel is substantially covered indiscriminately with a large number of the round metal pellets. Thereafter, the rubber panel I4 was inserted between the platens of a press for curing the rubber and embeddin the shot in the panel. In the typical exampl above referred to the panel hi was subjected to a pressure of 1350 lbs. per sq. in. between the electrically heated platens of a press, and held in the press at a temperature of about 320 F. for ten to twelve minutes. Thereafter, the Holland cloth may be stripped from the panel member l4, and the uncovered surface applied by any suitable adhesive to the tension surface of the leaf spring. As before, inserts, such as above described, are arranged between the opposed surfaces at the ends of adjacent spring leaves of a leaf spring, either between all of the leaves or selected pairs of the leaves as may be desired.

In a leaf spring constructed at last, the metal pellets lying at the surface of the panel member I4 engage the adjacent surfaces of the leaves and serve to reduce friction between the leaves, and the rubber panel provides a resilient support for the metal pellets and the ends of adjacent leaves.

While I have shown and described what I consider to be preferred embodiments of my invention, it will be understood that certain modifications may be made therein without departing from the spirit and scope of my invention.

I claim:

1. An anti-friction insertable member for use in the construction of a multi-leaf spring or the like adapted to be inserted between adjacent leaves of said spring, comprising in combination,

a single ply strip of tape, an adhesive coating on one surface of said tape, of the thickness of .025 inch; a plurality of globular metal pellets arranged indiscriminately across said adhesive coating and held thereby to cover one surface of said tape, and a coating of pressure sensitive adhesive covering the opposite surface of said tape from that supporting said pellets to thereby provide means for securing said tape to the outer end concave surfaces of at least one of said springs leaves.

2. A leaf spring construction of the class described, comprising, a plurality of concavoconvex metal leaf members arranged in stacked, superposed relation, and tape members inserted between end portions of adjacent leaf members, said tape members each having one surface thereof indiscriminately covered by a plurality of substantially spherical metal pellets and having the opposite surface thereof secured by adhesive to the concave surface of an overlying adjacent leaf member.

3. A composite leaf spring structure comprising, a plurality of concavo-convex metal leaf members arranged in stacked, superposed relation, and anti-friction tape members inserted between end portions of adjacent leaf members, said tape members each having a plurality of metal pellets adherently secured to and indiscriminately arranged over one surface thereof, and additionally having a pressure sensitive adhesive coating the opposite surface thereof for securing the same to the concave surface of an overlying one of said adjacent leaf members.

HAROLD E. CHURCHILL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,321,986 Daley Nov. 18, 1919 1,368,514 Linaburry Feb. 15, 1921 1,502,167 Weston July 22, 1924 1,521,020 Gullborg Dec. 30, 1924 1,542,055 Gullborg June 16, 1925 FOREIGN PATENTS Number Country Date 736,251 France Sept. 13, 1932 

